Thin film transistor liquid crystal display and method for manufacturing the same

ABSTRACT

There is provided a reflection type/transflection type thin film transistor liquid crystal display, including an insulating substrate, a thin film transistor formed on the insulating substrate, a transparent electrode made of indium-tin-oxide formed on the thin film transistor and electrically contacted with a source region and a drain region of the thin film transistor, and a curved conducting structure with an inclination of 3 to 20 degrees formed on the transparent electrode.

RELATED APPLICATIONS

[0001] The present invention is a divisional of co-pending U.S. patentapplication Ser. No. 10/139,852, filed May 7, 2002 which is incorporatedby reference as if fully set forth, and which claims priority toTaiwanese (R.O.C.) Patent Application No. 90120948 filed on Aug. 24,2001.

FIELD OF THE INVENTION

[0002] The present invention is related to a liquid crystal display(LCD), and more particularly, the present invention is related toreflection type/transflection type thin film transistor liquid crystaldisplay and the manufacturing process thereof.

BACKGROUND OF THE INVENTION

[0003] With the increasing progress in the manufacturing technique offlat panel display, liquid crystal display (LCD) has been extensivelyemployed as a main stream display device. The LCD uses electric field tocontrol the alignment of the liquid crystal molecules in the liquidcrystal layer, and determine whether the polarized light can passthrough the liquid crystal layer to make a dark display or a whitedisplay. As a result, how to get a brighter display for LCD has become asignificant target for the research on the manufacturing process of theliquid crystal display device.

[0004] For a reflection type or a transflection type thin filmtransistor liquid crystal display (TFTLCD), its brightness is determinedby the incident light emitted from a light source and the reflectinglight thereof. If it is desirable to obtain a brighter display, theintensity of light scattering in a direction perpendicular to thedisplay screen has to be increased. For this purpose the reflectivecharacteristic of the reflector thereof has to be intensified. As shownin FIG. 1(a), a resin coating 114 comprised of a plurality oftransparent resin beads 113 having a penetrative characteristic isformed on a first transparent electrode layer 111, in order that whenlight passes through the first transparent electrode layer 111 and thecolor filter 112 and enters the resin coating 114, a deflection is madeto the light departing from the resin coating 114 due to the collisionsagainst the transparent resin beads 113. Further the light is scatteredby way of the electric field applied between the second electrode layer116 on the TFT array substrate 115 and the first transparent electrodelayer 111, and the scattered light is then reflected by the reflector117. The conventional reflection type/transflection type TFTLCD of FIG.1(a) is advantageous in terms of the increase in the light scatteringangle, and thus the direction of reflection is easy to be controlled.However, the reflection type/transflection type TFTLCD of FIG. 1(a) isdisadvantageous by that the direction of light scattering is quitedifficult to be controlled precisely by adjusting the locations of thetransparent resin beads 113.

[0005] To solve the foregoing drawbacks experienced by the prior art, anovel manufacturing process for the reflection type/transflection typeTFTLCD that forms the resin coating directly on the second electrodelayer on the TFT array substrate has been addressed. As shown in FIG.1(b), when light passes through the color filter 122, light scatteringeffect will come about due to the electric field applied between thesecond electrode layer 126 and the first electrode layer 121. Thescattered light will then be reflected by the resin coating 124. Becausethe resin coating 124 is a curved structure, its uneven surface can beused to regulate the magnitude of the angle of reflection, and therebythe direction of reflection can be effectively controlled.

[0006] Though the prior art uses a resin coating to increase theintensity of light scattering in a direction perpendicular to thedisplay screen, the manufacturing cost of the reflectiontype/transflection type TFTLCD is quite expensive and the manufacturingprocess is quite complex (with one more photomask required). Indeed, howto reduce the manufacturing cost and simplify the manufacturing processof the conventional reflection type/transflection type TFTLCD is a majorobject of advancing the development of the manufacturing technique ofthe existing display device. The present invention can satisfy theseneeds.

SUMMARY OF THE INVENTION

[0007] An object of the present invention is to provide a manufacturingprocess for a thin film transistor liquid crystal display, comprisingthe steps of: (a) providing an insulating substrate, (b) forming a thinfilm transistor the insulating substrate and forming a transparentelectrode on the thin film transistor, wherein the transparent electrodeis electrically contacted with a source region and a drain region of thethin film transistor, (c) forming a conducting layer on the transparentelectrode layer, and (d) etching the conducting layer to define a curvedstructure with an inclination on the transparent electrode.

[0008] Preferably, the angle of the inclination may be ranged from 3 to20 degrees, and the curved structure may be shaped into an awl-shapedstructure or a conical structure.

[0009] Another object of the present invention is focused on theprovision of a manufacturing process for a thin film transistor liquidcrystal display, comprising the steps of: (a) providing an insulatingsubstrate, (b) forming a gate structure on a portion of the insulatingsubstrate, (c) forming an insulating layer on the insulating substrateand the gate structure, (d) forming a first semiconductor structure anda second semiconductor structure on the insulating layer, (e) forming aconducting layer on the insulating layer and the second semiconductorstructure, (f) etching the conducting layer to define a source regionand a drain region and a curved structure with an inclination on theinsulating layer, and (e) forming a transparent electrode on the curvedstructure, wherein the transparent electrode is electrically contactedwith a source region and a drain region of the conducting layer.

[0010] A further object of the present invention is involved with a thinfilm transistor liquid crystal display, including an insulatingsubstrate, a thin film transistor formed on the insulating substrate, atransparent electrode formed on the insulating substrate and the thinfilm transistor and electrically contacted with a source region and adrain region -of the thin film transistor, and a curved structure withan inclination formed on the transparent electrode.

[0011] It is still an object of the present invention to provide a thinfilm transistor liquid crystal display, including an insulatingsubstrate, a thin film transistor formed on the insulating substrate, acurved structure with an inclination formed on the insulating substrate,and a transparent electrode formed on the curved structure.

[0012] Now the foregoing and other features and advantages of thepresent invention will become more apparent through the followingembodiments with reference to the accompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIGS. 1(a) and 1(b) are cross-sectional views schematicallyillustrating the reflection type/transflection type TFTLCD according tothe prior art;

[0014] FIGS. 2(a) to 2(h 2) are cross-sectional views schematicallyillustrating the manufacturing steps involved in the production ofTFTLCD according to a first preferred embodiment of the presentinvention; and

[0015] FIGS. 3(a) to 3(g 4) are cross-sectional views schematicallyillustrating the manufacturing steps involved in the production ofTFTLCD according to a second preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] The manufacturing steps involved in the production of the TFTLCDaccording to a first preferred embodiment of the present invention canbe best understood in virtue of the following descriptions and thecross-sectional views of FIGS. 2(a) to 2(h 2). Referring to FIG. 2(a),an insulating substrate 211 is provided and a conducting layer (whichcan be formed from chromium, tungsten molybdenum, tantalum, aluminum orcopper) is formed onto the insulating substrate 211, and a firstphotomask lithography and etching process is performed define a gatestructure 212 on the insulating substrate 211. In FIG. 2(b), aninsulating layer 233, a first semiconductor layer 214 (which is commonlymade of an amorphous-silicon layer) and a second semiconductor layer 215(which is commonly made of a highly-doped N+ amorphous-silicon layer)are sequentially formed on the gate structure 212 and the substrate 211.As shown in FIG. 2(c), a second photorask lithography and etchingprocess is performed to remove a portion of the first semiconductorlayer 214 and the second semiconductor layer 215, so as to define afirst semiconductor structure 216 and a second semiconductor structure217 on a portion of the insulating layer 213. As shown in FIG. 2(d), aconducting layer 218 is deposited onto the second semiconductorstructure 217 and the insulating layer 213. As shown in FIG. 2(e), athird photomask lithography and etching process is performed to remove aportion of the conducting layer 218 and the second semiconductorstructure 217. An opening 219 exposing a portion of the surface of thefirst semiconductor structure 216 is formed in the conducting layer 218,and a source region and a drain region 220 are respectively defined onthe opposite sides of the opening 219. In FIG. 2(f), a passivation film221 (which is commonly made of silicon nitride) is formed to cover thedrain and source region 220, and a fourth photomask lithography andetching process is performed to define a contact window 222. Referringto FIG. 2(g), a transparent electrode layer commonly made ofindium-tin-oxide (ITO) is formed on the passivation film 221, and afifth photomask lithography and etching process is performed to define atransparent pixel electrode 233. FIGS. 2(h 1) and 2(h 2) respectivelyshow that a conducting layer is formed onto the transparent pixelelectrode 233, and a sixth photomask lithography and etching process isperformed to define awl-shaped conducting structures 224 and conicalconducting structures 225 on the transparent pixel electrode 223. Withthe variation of the parameters of the concentration of the etch agent,etching time, temperature and so on, awl-shaped conducting structures224 or conical conducting structures 225 that are of different awl-likeprofiles may be formed on the transparent pixel electrode 223. MorePreferably, both of the awl-like conducting structures 224 and 225 havean inclination of 3 to 20 degrees, and thereby the light scatteringangle can be adjusted appropriately.

[0017] The formation steps of the TFTLCD according to a second preferredembodiment of the present invention can be best understood in virtue ofthe following descriptions and the cross-sectional views of FIGS. 3(a)to 3(g 4). Referring to FIG. 3(a), an insulating substrate 311 isprovided and a conducting layer (which can be formed from chromium,tungsten molybdenum, tantalum, aluminum or copper) is formed on theinsulating substrate 311, and a first photomask lithography and etchingprocess is then performed to define a gate structure 312 on theinsulating substrate 311. Next, as shown in FIG. 3(b), an insulatinglayer 313, a first semiconductor layer 314 (which is commonly made of anamorphous-silicon layer) and a second semiconductor layer 315 (which iscommonly made of a highly-doped N+ amorphous-silicon layer) aresequentially formed on the gate structure 312 and the substrate 31. Asshown in FIG. 3(c), a second photomask lithography and etching processis performed to remove a portion of the first semiconductor layer 314and the second semiconductor layer 315, so as to define a firstsemiconductor structure 316 and a second semiconductor structure 317 ona portion of the insulating layer 313. As shown in FIG. 3(d), aconducting layer 318 is deposited onto the second semiconductorstructure 317 and the insulating layer 313. As shown in FIGS. 3(e 1) and3(e 2), a third photomask lithography and etching process is performedto remove a portion of the conducting layer 318 and the secondsemiconductor structure 317. An opening 319 exposing a portion of thesurface of the first semiconductor structure 316 is formed in theconducting layer 318, and a source region and a drain region 320 arerespectively defined on the opposite sides of the opening 319. In FIG.3(e 1), a fourth photomask lithography and etching process is performedto define awl-shaped conducting structures 3211 on the insulating layer313. In FIG. 3(e 2), a fourth photomask lithography and etching processis performed to define conical conducting structures 3212 on theinsulating layer 313. With the variation of the parameters of theconcentration of the etch agent, etching time, temperature and so on,awl-shaped conducting structures 3211 or conical conducting structures3212 that are of different awl-like profiles may be formed on theinsulating layer 313. More preferably, both of the awl-like conductingstructures 224 and 225 have an inclination of 3 to 20 degrees, andthereby the light scattering angle can be adjusted appropriately. FIGS.3(f 1) and 3(f 2) respectively shows that after the source and drainregion 320 are defined, a passivation film 321 (which is commonly madeof silicon nitride) is formed to cover the drain and source region 320,and a fifth photomask lithography and etching process is performed todefine a contact window 322. FIGS. 3(g 1) and 3(g 2) respectively showsthat after a transparent electrode layer commonly maze ofindium-tin-oxide (ITO) is deposited onto the passivation film 321 andthe awl-like conducting structures 3211 and 3212, a sixth photomasklithography and etching process is performed to define a transparentpixel electrode 3231 and 3232.

[0018] The formation of the awl-like conducting structures as mentionedabove can be further illustrated by the following manufacturing steps toget a better understanding to the present invention.

[0019] First, a double-layer metal film is deposited, for example, amolybdenum-chromium alloy thin-film of a thickness of 200 nm isdeposited as the bottom layer, and an aluminum alloy thin-film of athickness of 50 nm is deposited on the molybdenum-chromium alloythin-film as a top layer. With the use of photomask to perform exposureand development steps to define the pattern of the area that is to bereserved, an etching step is then performed with a mixed-acid based etchsolution, for example, the mixture of phosphoric acid (H₃PO₄), nitricacid (HNO₃) and/or acetic acid (CH₃CCOH) to etch the double-layer metalfilm, so as to define awl-like conducting structures with aninclination. The angle of the inclination may be controlled by adjustingthe over-etching time in cooperation with the photomask of anappropriate line width (about 3 μm to 10 μm), and further awl-shaped orconical conducting structures can be created as desired.

[0020] A preferable aspect of the present invention is to provide areflection type/transflection type TFTLCD. Therefore, the transparentelectrode layer made of ITO can be served for a third conducting layer.FIGS. 3(g 3) and 3(g 4) respectively show that after the thirdconducting layer is deposited onto the passivation film 321 and theawl-like conducting structures (3211,3212), a sixth photomasklithography and etching process is performed to define a pixel areaconstituted by transparent electrode (3233,3234).

[0021] In conclusion with the above statements, it can be readilyunderstood that the present invention is superior to the prior art interms of the inclusion of the awl-like conducting structures with aninclination. Because the awl-like conducting structures is provided withan inclination, the magnitude of the light reflecting angle can beadjusted and the direction of reflection can be controlled efficiently.More specifically, with the introduction of the present invention, themanufacturing process of the thin film transistor liquid crystal displaycan be simplified by eliminating one photomask lithography and etchingprocess compared with the prior art, and the manufacturing cost can beslashed due to the removal of the costly resin coating.

[0022] Those of skill in the art will soon recognize that these andother modifications can be made within the spirit and scope of thepresent invention as further defined in the appended claims.

What is claimed is:
 1. A method of manufacturing a thin film transistorliquid crystal structure comprising the steps of: (a) providing aninsulating structure; (b) forming a gate structure on a portion of saidinsulating substrate; (c) forming an insulating layer on said gatestructure and said insulating substrate; (d) forming a firstsemiconductor structure and a second semiconductor structure on saidinsulating layer; (e) forming a conducting layer on said insulatinglayer and said second semiconductor structure; (f) etching saidconducting layer to define a source region and a drain region and acurved structure with an inclination; and (g) forming a transparentelectrode on said curved structure, wherein said transparent electrodeis electrically contacted with said source region and said drain region.2. The method of claim 1 wherein an angle of said inclination is about 3to 20 degrees.
 3. The method of claim 1 wherein said conducting layer isformed from a metallic material.
 4. The method of claim 1 said curvedstructure is an awl-shaped structure.
 5. The method of claim 1 whereinsaid curved structure is a conical structure.
 6. The method of claim 1wherein said transparent electrode is formed from indium-tin-oxide.
 7. Athin film transistor liquid crystal display comprising: an insulatingsubstrate; a thin film transistor formed on said insulating substrate; acurved structure with an inclination formed on said insulatingsubstrate; and a transparent electrode layer formed on said curvedstructure.
 8. The thin film transistor liquid crystal display of claim 7wherein an angle of said inclination is about 3 to 20 degrees.
 9. Thethin film transistor liquid crystal display of claim 7 wherein saidcurved structure is an awl-shaped structure.
 10. The thin filmtransistor liquid display of claim 7 wherein said curved structure is aconical structure.
 11. The thin film transistor liquid display of claim7 wherein said transparent electrode is formed from indium-tin-oxide.